This invention relates to devices used to manipulate continuous well strings for wellsite operations. Continuous well strings include rod, used for example to operate downhole pumps, and continuous tubing, used for example in a variety of downhole applications such as drilling and clean out operations. Continuous well strings are manipulated downhole typically with continuous chain injection units that include gripper pads for gripping the well strings. One early such design is shown in U.S. Pat. No. 3,559,905 of Palynchuk, issued Feb. 1, 1971, in which a continuous chain with gripping blocks carried by the chain is used to inject the well string into the well. More recently, such continuous chain gripper systems have been described in U.S. Pat. No. 5,553,668 of Council, et al, issued Sep. 10, 1996.
The continuous chain injection units when used at a rig conventionally are provided with their own hydraulic power supply, separate from the rig power supply. In addition, these conventional power supplies provide complicated ways of changing the speed of the motors. This invention provides an improvement on such power supplies.